In the conventional process for manufacturing a secondary cell such as a lithium ion secondary cell, a wound body obtained by winding a positive electrode, a negative electrode, and separators is housed in a transversely oriented posture in an outer case.
Further, in the process for manufacturing a secondary cell, an electrolytic solution is poured into the outer case, a cell case is then hermetically closed, and the wound body is impregnated with the electrolytic solution.
With the technique disclosed in Patent Literature 1, an opening of a case (cell case) is closed, the pressure inside the case is reduced, and an electrolytic solution is poured into the depressurized case.
With the technique disclosed in Patent Literature 1, the pressure inside the case is raised to a pressure higher than the atmospheric pressure to impregnate the wound body with the electrolytic solution, while pouring the electrolytic solution (or at the same time of pouring of the electrolytic solution).
Immediately after the pouring, the electrolytic solution permeates into both axial end portions of the wound body due to a capillary effect. As a result, a hermetically closed space is formed inside the wound body.
When the pressure inside the case is raised while pouring the electrolytic solution, as with the technique disclosed in Patent Literature 1, the air inside the pressurized case pushes away the electrolytic solution which has permeated in the both axial end portions of wound body, as depicted in FIG. 20, and the air can penetrate into the wound body (see the arrows in FIG. 20).
In other words, in this case, the air can remain in the air introduction path and in the axially central portion of the wound body.
As described hereinabove, with the technique disclosed in Patent Literature 1, the wound body cannot be effectively impregnated with the electrolytic solution.